From an article in Shotgun Sports, March 2005, "Civil War Shotgun Soldiers" by Keith M. Bennett....
Mr Bennett describes the armaments thusly " The flower of the state rushed to him in response to his call, in numbers more than wanted SELF EQUIPPED - EACH MAN WITH TWO 'NAVY SIX' PISTOLS, A BOWIE, AND DOUBLE BARRELED SHOTGUN,and everything ready for action, from spurs to the lariat tethered to the horn of the saddle"
My mistake qwa that I thought each man also had 2 double barreled shotguns.
The point of this article is that the 8th signifies the beginning of the combat shotgun